Electronically tunable microwave filters have found wide applications in microwave systems. Compared to mechanically and magnetically tunable filters, electronically tunable filters have an advantage of fast tuning capability over wide band applications. Because of this advantage, they can be used in the applications such as cellular, PCS (personal communication system), Point to Point, Point to multipoint, LMDS (local multipoint distribution service), frequency hopping, satellite communication, and radar systems. In the electronically tunable filters, filters may be divided into two types: one is a dielectric capacitor based tunable filter and the other is semiconductor varactor based tunable filter. Compared to semiconductor varactor based tunable filters, tunable dielectric capacitor based tunable filters have the merits of lower loss, higher power-handling, and higher IP3, specifically at higher frequencies.
Thus, there is a strong need for tunable filters which have low insertion loss, fast tuning speed, and high power handling.